This question is often raised in chat. The quick answer is: there is none.
Race selection is completely based on the preference of the player. Most players choose the race based on which avatar, or displayed image, they would like associated with their character. Characters who wish to portray evil characters generally join the reapers to take advantage of their more evil-looking portraits. Ladies wishing to be alluring will often stay with the elven line (or the reaper`s ghoul line).
Each race does give a small stat bonus based on the race. This bonus is rather small compared to the number of stat points gained during your ascension to max level (currently 1000 levels and 10,000 sublevels). However, if you are the type of player who wants to maximize their stats at all costs, then choosing an appropriate race for your profession may make sense.
To fully maximize your stats, choose a race that boosts those stats most important to your profession. Magic users will want to choose a race that gives a bonus to intelligence and mana, while warriors will choose strong races with hitpoints or stamina. Rogues and archers may also choose races that give bonus to dexterity or speed, depending upon their weapon of choice.
Keep in mind that you can choose to display any portrait from your racial line as your character`s avatar. After evolving into a giant, you can still opt to display the ogre, orc, dwarf as your avatar (but not the human). Those with the ability to disguise have a much broader selection of portraits to use, and for a fee, an artist can create a custom avatar for you to use (check if an artist is available before making this selection - they have been scarce lately).